The invention relates to a method for the continuous conditioning of a cell suspension, in the case of which the cell suspension is centrifuged and the separated components of the cell suspension are separately removed.
The invention furthermore relates to an apparatus for performing a method for the conditioning of a cell suspension, more particularly the above mentioned method, comprising a centrifuge, which has at least one separation chamber with an annular duct, a supply duct for the cell suspension, a drain duct for a high purity cell concentrate to be produced and a drain duct for components of the cell suspension which are not needed.
In the prior art many proposals have been made for such separation apparatus and corresponding method, in the case of which more particularly blood is separated into its components and the latter, for instance erythrocytes or plasma, are put to a further use.
There are many medical applications for such methods and apparatus. One of these fields of application is intraoperative autotransfusion, which represents a transfusion technique economizing in the use of extraneous blood and which has found wide application in the last ten years. Intraoperative auto-transfusion is a method for the retransfusion of blood collected from the operation site. Within the field of intraoperative autotransfusion so-called "whole blood transfusion methods" are able to be employed which only involve particle filtration of the collected blood, while more involved methods are the plasma separation and washing methods, which lead to a washed erythrocyte concentrate for retransfusion. The advantages of transfusion of autologous blood, that is to say blood from the patient as opposed to blood from another source (homologous blood) lie in the prevention of infectious diseases such as for example AIDS, hepatitis or others, and furthermore in the prevention of transfusion reactions owing to biological incompatibility and immune system reactions.
As part of the development of intraoperative autotransfusion techniques it has been found that transfusion of whole blood may have disadvantages as compared with transfusion of washed erythrocyte concentrates. These disadvantage of whole blood transfusion methods are that undesired components of the collected blood cannot be eliminated. Intraoperative blood contains unknown quantities of hemolysis products, extraneous components leached into the tissues or coming from the outside, excess volume, anticoagulants, activated plasmatic and cellular coagulation factors, products resulting from coagulation activation and of the fibrinolytic system. All these components may be responsible for clinical complications which in turn lead to a limitation of the field of application. In the prior art there have been suggestions to utilize filter systems in such autotransfusion systems for blood, which however only retain blood clots or pieces of tissue. Such a system is proposed in the U.S. Pat. No. 4,014,329. The U.S. Pat. No. 4,886,487 describes an apparatus for the separation of excess fluid, in which respect however coagulation factors, washing liquid, anticoagulant and other additives are returned with the blood to the patient.
As an alternative to whole blood transfusion plasma separation methods and plasma separation methods in combination with washing methods, or washing methods alone, have been developed, which use centrifuges. Such method are described in the German patent publication 2,262,856 A and the patent publication WO 89/01792. These centrifuges do however suffer from the disadvantage that they operate discontinuously. The individual method steps for the treatment of the blood and for retransfusion take place one after each other in time, such treatment having to take place in relatively large units with a completely filled chamber in order to ensure the functional operability of the method. Thus for example it is necessary to collect 225 ml of erythrocyte concentrate in a centrifuge.
The disadvantages of such discontinuous methods of operating are to be seen more specifically in the large initial volume, which is necessary for each respective conditioning stage. The treatment of small quantities, as is for instance necessary in pediatrics, is consequently not possible at all. A further, substantial disadvantage of such discontinuously operating methods is to be seen in the slow rate of processing, which is caused by the sequential performance of the individual method steps.
It is therefore to be seen that known methods and equipment are not suitable for continuous conditioning of a cell suspension as necessary in the case of an intraoperative autotransfusion.
The German patent publication 3,817,664 C describes a counter-current extraction centrifuge in which whole blood is centrifuged in the opposite direction to a washing solution. Neither the apparatus nor the method are however able to fulfill the requirements which arise in the case of autotransfusion, since undesired components are not separated in a reliable and effective manner.
The most relevant prior art as regards the apparatus is constituted by the European patent publication 155 684 B1, which describes a device for the separation of blood and provides for a return of low-thrombocyte plasma in order to dilute the whole blood feed. For the fields of application in question this equipment is however not able, to be employed, since there is no suitable supply duct system in the separation chamber here.
The U.S. Pat. No. 4,010,894 shows a centrifuge with an annular duct, which renders possible a multi-stage manner of operation with the possibility of separate removal of red blood cells, plasma and further blood components. This device is not suitable for the purpose of the invention either, because there is no sufficient separation if the desired components of the cell suspension. The cell concentrate can not be subjected to a washing operation, something that is essential for sufficient separation.